JP5437253B2 - Fabrication of red and white nitride based LEDs without phosphors - Google Patents

Description

  The present invention relates generally to a multiple quantum well structure for a light emitting diode and a method of making a multiple quantum well structure for a light emitting diode.

  Light emitting diodes (LEDs) can function as illumination sources and are typically used for applications such as outdoor full color displays, traffic lights, data storage, solid state lighting and communications. Typically, Group III nitride based LEDs emit light of a wavelength corresponding to the band gap of the indium gallium nitride / gallium nitride (InGaN / GaN) multiple quantum well (MQW) layer. Light is generated when a bias is applied across the pn junction of the GaN layer. In the LED, holes and electrons injected by the p-type and n-GaN layers are combined in the active layer to emit light from the LED surface.

  For example, when a high In content is incorporated for long wavelength applications such as green or yellow LEDs, epitaxial growth of InGaN / GaN MQW becomes a practically difficult problem. In addition, light emission efficiency is usually lowered in light emission in which the wavelength is increased by incorporating high In. Although the amount of In taken in can be increased by lowering the growth temperature, usually the crystal quality deteriorates at a lower temperature, so that the photoluminescence (PL) intensity is lowered.

  InGaN quantum dots have been studied to increase the quantum efficiency of LEDs (see, eg, WO 2004/054006 A1 by CHOI et al.). The color emitted from the LED can be adjusted from blue to orange by controlling the size of the quantum dots (see, for example, US Pat. No. 6,445,009 B1 by Grandjean et al.). DenBaars et al. In US Patent Application No. 2006/0255347 A1 describes doping GaN with one or more rare earth transition elements to obtain tunable LEDs having various shades. These transition elements include Cr, Ti, and Co, and it has been proposed that white light can be generated using a combination of these elements. However, it is practically difficult to control the depth of implantation into the thin active layer of the MQW structure.

  Chua et al., In U.S. Patent Application No. 2004/0023427 A1, describe white light emission using InGaN quantum dots incorporated in the well layer of the MQW structure of the LED. However, when high temperature in-situ annealing was performed to activate the p-dopant magnesium (Mg), external diffusion of quantum dots into the well layer or barrier layer occurred. This usually makes the MQW layer unclear. As a result, the confinement effect by the quantum dots may be compromised. Furthermore, in US Patent Application No. 2004/0023427 A1, the color of light emitted from the LED cannot be accurately controlled, and the whiteness of the LED varies.

  At present, visible red-orange light sources and yellow light sources are usually obtained based on aluminum indium gallium phosphate (AlInGaP) materials, whereas light green, blue and purple LEDs are usually made from GaN-based material systems Is done. However, with current technology, it is not known that GaN-based LEDs typically have the red emission necessary to provide a red component to produce white emission.

  Usually, to generate white light from an LED, a combination of separate LEDs, each emitting a separate color, red, green and blue light, is used. Alternatively, individual blue and yellow LEDs are combined to produce white light. One disadvantage is that multiple LEDs of different materials are used to generate white light, which increases the complexity of the fabrication technology and the overall fabrication cost. Since different diode types use different applied voltages, the resulting device typically uses complex control electronics. Furthermore, different degradation rates of the materials used, such as AlInGaP (for red emission) and InGaN (for green and blue emission) usually affect the reliability or quality of the resulting white light. With regard to an alternative fabrication method that uses a blue LED coated with a yellow phosphor for white light generation, degradation of the phosphor causes the above-mentioned reliability / quality problems. Also, the use of phosphors usually increases manufacturing costs and reduces external quantum efficiency due to absorption in the phosphors.

International Publication No. 2004/054006 A1 US Pat. No. 6,445,009 B1 US Patent Application No. 2006/0255347 A1 US Patent Application No. 2004/0023427 A1

  Accordingly, there is a need for a multiple quantum well (MQW) structure for light emitting diodes and a method of making an MQW structure for light emitting diodes to address at least one of the above-mentioned problems.

  According to a first aspect of the present invention, there is provided a multiple quantum well (MQW) structure for a light emitting diode, the MQW structure comprising a plurality of quantum well structures, each quantum well structure comprising: a barrier layer; And a well layer incorporating quantum dot nanostructures formed on the barrier layer, the barrier layer and the well layer including a first metal nitride-based material, wherein at least one of the quantum well structures is on the well layer Further comprising a capping layer formed, the capping layer comprising a second metal nitride based material having a different metal element compared to the first metal nitride based material.

  Individual quantum well structures can further include a wetting layer formed between the barrier layer and the well layer to facilitate the formation of quantum dot nanostructures.

  At least one of the quantum well structures can further include a second capping layer formed on the capping layer, wherein the second capping layer is different compared to the second metal nitride based material. A third metal nitride based material having a metal element is included.

  The MQW structure may further include a p-type contact structure formed on the outermost structure of the plurality of quantum well structures, and the p-type contact structure is formed on the electron blocking layer and the electron blocking layer. And a p-type metal nitride layer.

  The p-type metal nitride layer can include an indium (In) material.

  The p-type metal nitride layer can be formed using a temperature between about 750 ° C. and 800 ° C.

The MQW structure can further include an n-type contact layer for making electrical contact with the n ⁺ layer underlying the plurality of quantum well structures.

  The MQW structure can emit red / yellow light.

  The MQW structure can emit red light.

  The capping layer can include an aluminum nitride (AlN) material.

  The thickness of the capping layer can be kept up to about 3 nm.

  The quantum dot nanostructure can include indium gallium nitride (InGaN) quantum dots.

  According to a second aspect of the present invention, a light emitting diode structure is provided, the light emitting diode structure comprising a red / yellow light emitting multiple quantum well (MQW) structure, wherein the individual quantum well structures of the red / yellow light emitting MQW are: A quantum well of red / yellow light emitting MQW comprising a barrier layer and a well layer formed on the barrier layer and incorporating a quantum dot nanostructure, the barrier layer and the well layer comprising a first metal nitride based material At least one of the structures further includes a capping layer formed on the well layer, the capping layer comprising a second metal nitride based material having a different metal element as compared to the first metal nitride based material. The light emitting diode structure further includes a blue light emitting MQW structure integrally formed with the red / yellow light emitting MQW to emit white light from the light emitting diode structure. No.

  The blue light emitting MQW structure can be formed on the outermost structure of the plurality of quantum well structures of the red / yellow light emitting MQW structure.

  The innermost structure of the plurality of quantum well structures of the red / yellow light emitting MQW structure can be formed on the blue light emitting MQW structure.

The light emitting diode structure includes an n-type contact layer for making electrical contact with the n ⁺ layer under the red / yellow light emitting and blue light emitting MQW structures, and a red / yellow light emitting MQW structure and a blue light emitting MQW structure, respectively. Each of the p-type contact structures may further include an electron blocking layer and a p-type metal nitride layer formed on the electron blocking layer.

The light emitting diode structure includes an n-type contact layer for making electrical contact with the n ⁺ layer under the blue light emitting MQW structure, and a p-type formed on the blue light emitting MQW structure for activating the blue light emitting MQW structure. A contact layer, and the red / yellow light emitting MQW structure can emit red / yellow light based on absorption of blue light emission from the blue light emitting MQW structure.

  The capping layer can include an aluminum nitride (AlN) material.

  The thickness of the capping layer can be kept up to about 3 nm.

  The quantum dot nanostructure can include indium gallium nitride (InGaN) quantum dots.

  According to a third aspect of the present invention, a light emitting diode structure is provided, the light emitting diode structure comprising a red / yellow light emitting multiple quantum well (MQW) structure, wherein the individual quantum well structures of the red / yellow light emitting MQW are: A quantum well of red / yellow light emitting MQW comprising a barrier layer and a well layer formed on the barrier layer and incorporating a quantum dot nanostructure, the barrier layer and the well layer comprising a first metal nitride based material At least one of the structures further includes a capping layer formed on the well layer, the capping layer comprising a second metal nitride based material having a different metal element as compared to the first metal nitride based material. The light emitting diode structure further includes a blue light emitting MQW structure and a green light emitting MQW structure, and the blue light emitting MQW structure and the green light emitting MQW structure are It is formed on the red / yellow light emitting MQW integral to emit white light from the diode structure.

  The red / yellow light emitting MQW structure can be formed on the blue light emitting MQW structure and the green light emitting MQW structure.

The light emitting diode structure activates an n-type contact layer for making electrical contact with the n ⁺ layer under the red / yellow light emitting, blue light emitting and green light emitting MQW structures, and a blue light emitting MQW structure and a green light emitting MQW structure, respectively. And a p-type contact structure formed on the blue light-emitting MQW structure and the green light-emitting MQW structure, respectively, wherein the p-type contact structure is formed on the electron blocking layer and the electron blocking layer, respectively. And a red / yellow light emitting structure based on absorption of blue light emission from the blue light emitting MQW structure, green light emission from the green light emitting MQW structure, or both. Can emit red / yellow light.

  The capping layer can include an aluminum nitride (AlN) material.

  The thickness of the capping layer can be kept up to about 3 nm.

  The quantum dot nanostructure can include indium gallium nitride (InGaN) quantum dots.

  According to a fourth aspect of the present invention, there is provided a method of making a multiple quantum well (MQW) structure for a light emitting diode, the method comprising a barrier layer and a quantum dot nanostructure each formed on the barrier layer. Forming a plurality of quantum well structures, wherein the barrier and well layers include a first metal nitride based material, and comparing the first metal nitride based material to the first metal nitride based material. Forming at least one of the quantum well structures to further include a capping layer on the well layer including a second metal nitride-based material having different metal elements.

  According to a fifth aspect of the present invention, there is provided a method of making a light emitting diode structure, the method comprising a barrier layer and a well layer each formed on the barrier layer and incorporating a quantum dot nanostructure, Forming a plurality of quantum well structures in which the barrier and well layers include a first metal nitride-based material, and a second metal element having a different metal element compared to the first metal nitride-based material. Forming at least one of a red / yellow MQW quantum well structure to further include a capping layer comprising a metal nitride-based material on the well layer; and red / yellow to emit white light from the light emitting diode structure. Forming a blue light emitting MQW structure integrally with the yellow light emitting MQW.

  According to a sixth aspect of the present invention, there is provided a method of making a light emitting diode structure, the method comprising a barrier layer and a well layer each formed on the barrier layer and incorporating a quantum dot nanostructure, Forming a plurality of quantum well structures in which the barrier and well layers include a first metal nitride-based material, and a second metal element having a different metal element compared to the first metal nitride-based material. Forming at least one of a red / yellow MQW quantum well structure to further include a capping layer including a metal nitride-based material on the well layer; and integrating the blue light emitting MQW structure with the red / yellow light emitting MQW. Forming a green light emitting MQW structure integrally with the red / yellow light emitting MQW structure and the blue light emitting MQW structure in order to emit white light from the light emitting diode structure. And a flop.

  For those skilled in the art, embodiments of the present invention will be better understood and readily apparent from the following description, taken in conjunction with the drawings for illustrative purposes only.

It is the schematic which shows a monochromatic LED structure. FIG. 3 is a schematic diagram illustrating the formation of electrical contacts on a monochromatic LED structure. It is a graph of the intensity | strength versus wavelength which shows the electroluminescence spectrum of yellow LED. It is an intensity | strength versus wavelength graph which shows the electroluminescence spectrum of orange LED. It is a graph of intensity | strength versus wavelength which shows the electroluminescence spectrum of red LED. 1 is a schematic diagram illustrating an adjustable white LED structure. FIG. FIG. 6 is a schematic diagram illustrating the formation of electrical contacts on a tunable white LED structure. FIG. 4 is an intensity versus wavelength graph showing the electroluminescence spectrum of a “cold” white LED. FIG. 6 is a schematic diagram illustrating the formation of electrical contacts on another adjustable white LED structure. FIG. 6 is a schematic diagram illustrating yet another adjustable white LED structure. FIG. 3 is a schematic diagram illustrating the formation of electrical contacts on an adjustable LED structure. It is a graph of the current (I) versus voltage (V) which shows the IV measurement value obtained from the yellow LED structure and the white LED structure. It is a scanning electron microscope (SEM) image which shows the surface morphology of a white LED structure. 8 is a scanning electron microscope (SEM) image showing the surface morphology of a sample white LED structure having the structure schematically shown in FIG. 8 is an enlarged scanning electron microscope (SEM) image of a white LED structure having the structure schematically shown in FIG. FIG. 8 is a graph of intensity versus wavelength showing the electroluminescence spectrum of a white LED structure having the structure schematically shown in FIG. 8 is a graph of current (I) versus voltage (V) showing IV measurements obtained from a white LED structure having the structure schematically shown in FIG. FIG. 5 is a flow diagram illustrating a method for fabricating an MQW structure for a light emitting diode. It is a flowchart which shows the method of producing a light emitting diode. It is a flowchart which shows another method of producing a light emitting diode.

In the described example embodiment, the growth of the LED is performed using a metal organic chemical vapor deposition (MOCVD) apparatus. In the example embodiment, trimethylgallium (TMGa), trimethylindium (TMIn), trimethylaluminum (TMA), magnesium (Cp ₂ Mg) and silane (SiH ₄ ) are used as precursors. Hydrogen and nitrogen are used as carrier gases for effectively capturing elements on the LED surface.

  In an example embodiment, a multiple quantum well (MQW) structure is grown at a defined temperature with the incorporation of InGaN quantum dots on the InGaN well layer. The formed quantum well is then capped with a thin aluminum nitride (AlN) layer. Hereinafter, this embodiment will be described in detail.

The AlN layer can function as a cap layer for preventing external diffusion of InGaN quantum dots. The lattice constant of In _X Ga _1-X N or InN quantum dots is about 3.5446 angstrom (Å), whereas the lattice constant of the AlN layer is about 3.1114 (Å). Thereby, when compared with the GaN / InN system (about 10.6%), a larger lattice mismatch occurs in the AlN / InN system (about 13%). This larger lattice mismatch can further prevent outdiffusion of quantum dots when high temperatures are applied during subsequent layer growth and annealing processes. Since the AlN layer may generate a greater compressive stress for subsequent growth of the InGaN wells, we have intervened after the growth of the GaN barrier and before the growth of the InGaN quantum dots and InGaN well layers. It is not recommended to use an AlN layer as the layer. As a result, the uptake of indium and the blue shift of its emission wavelength can be weakened.

FIG. 1 is a schematic diagram illustrating a monochromatic LED structure 100 of this example embodiment. A sapphire substrate 102 is prepared in the processing chamber. To promote GaN nucleation on the sapphire substrate 102, a low temperature buffer layer 106 is grown on the substrate 102 to a thickness of about 26 nm at a temperature range of about 520 ° C. to 550 ° C. An n ⁺ layer 108 of GaN with a doping concentration of 10 ¹⁸ cm ⁻³ is grown on the layer 106 at a temperature of about 900 ° C. to 1050 ° C. After layer 108 is grown, GaN barrier layer 110 is grown to a thickness of about 5-15 nm with a Si doping concentration of about 2 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁸ cm ⁻³ . One skilled in the art will appreciate that although the barrier layer 110 can be grown without Si doping, Si doping may be preferred because the quality of the barrier layer 110 is usually improved with Si doping.

After the barrier layer 110 is grown, the temperature is lowered to about 700-750 ° C., and a thin wet layer 112 of In _X Ga _1-X N having a composition of x to 0.10-0.20 and a thickness of about 1 nm is formed. Growing on the barrier layer 110. The wetting layer 112 can facilitate the incorporation of indium nitride-rich quantum dots during the In burst process. After forming the thin wetting layer 112, the indium precursor TMIn flows over the substrate 102 at a flow rate of less than about 20 μmol / min for about 6-30 seconds, where 0.2 <w <1.0. Nanostructures such as _W Ga _1-W N 114 or “quantum dots” are formed. In atoms from the indium precursor TMIn can separate at the nitrogen dangling bonds of the InGaN wet layer and function as a seed layer for InGaN quantum dot growth such as 114 determined by the precursor flow rate. . To control the size of indium rich InGaN quantum dots such as 114, the amount of TMIn flow that acts as an anti-surfactant and the duration of the TMIn flow are monitored. The flow rate of TMIn is maintained at less than about 20 μmol / min, preferably about 20 sccm (4.5 μmol / min) to about 80 sccm (18.0 μmol / min), so that an In-rich InGaN quantum dot such as 114 can be obtained. Form.

After a quantum dot such as 114 is grown, an InGaN quantum well layer 116 is grown on the nanostructure such as 114 to form an embedded InGaN quantum dot / well layer 116 having a thickness of about 3-5 nm. The growth temperature of the In ^W Ga ^{1 -W} N well layer 116 is maintained at about 700 ° C. to 750 ° C. to provide an indium composition of 0.2 <w <0.5. The amount of indium incorporated depends on the desired emission color. In order to obtain monochromatic light emission, temperature fluctuations are minimized during the growth of MQW, the growth of quantum dots such as 114 and the well layer 116, and the like. After the well layer 116 is grown, the well layer 116 is capped with an AlN layer 118. The thickness of the AlN layer 118 is kept relatively thin as compared to the well layer 116 (preferably thinner than about 3 nm). In this example embodiment, after the InGaN well layer 116 is grown, a time interval of more than about 30 seconds is maintained before the AlN layer 118 is grown. For better crystal quality, the temperature for growing the AlN layer 118 and the GaN barrier layer 110 can be set about 0-30 ° C. higher than the temperature for growing the InGaN well layer 116. After the AlN layer 118 is grown, the GaN cap layer 120 is grown using substantially the same conditions as for growing the GaN layer 108.

  The barrier layer 110 to the GaN cap layer 120 form a red / yellow light emitting quantum well structure 122. In this example embodiment, the steps of forming the barrier layer 110 through the GaN cap layer 120 are repeated (see quantum well structure 124, etc.) to form a red / yellow light emitting multiple quantum well (MQW) structure 126.

  For those skilled in the art, only two quantum well structures 122 and 124 are shown in FIG. 1 for the sake of clarity, but the number of quantum well structures may range from 3 to 5 or the like. Will understand. As those skilled in the art will appreciate, forming more quantum well structures such as 122, 124 can improve the luminous intensity of the LED structure 100 and broaden the wavelength range.

  In this example embodiment, for example, when the next layer such as the GaN barrier layer 132 grows at a higher temperature, the AlN layer 118 having a lattice constant different from that of InGaN encapsulates and an In-rich layer such as 114 is formed. Diffusion of InGaN quantum dots into the well layer 116 or into the GaN barrier layer 132 of the next quantum well structure 124 can be prevented.

In order to grow the GaN cap layer 128 of the quantum well structure 124, the TMGa flow rate is set to be the same as the flow rate used to grow the next p-AlGaN layer, thereby substantially adjusting the TMGa flow. Will be continuous. After the GaN cap layer 128 is grown, the GaN layer 130 is grown to a thickness of about 15-30 nm with a Si dopant concentration of about 2 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ at a temperature of about 740 ° C. to 780 ° C. . The _{p-Al y Ga 1-y} N electron blocking layer 133 containing (0.1 <y <0.3 wherein) is grown to a thickness of about 20 to 50 nm. TMA flow for growing a _{p-Al y Ga 1-y} N is maintained at about 40~100μ mol / min at a growth temperature of about 750 to 800 ° C.. During growth, the Cp ₂ Mg source is maintained at about 0.15 to 0.5 μmol / min. The p-AlGaN layer 133 can function to prevent electrons from traversing into the p-AlGaN region 134 to enable effective recombination in the MQW structure 126.

  As those skilled in the art will appreciate, p-GaN is typically grown at temperatures below 900 ° C. and in the range of about 760-825 ° C. to prevent out-diffusion of quantum dots. However, as a result, the p-type conductivity is lowered and the crystal quality is deteriorated. In this example embodiment, p-GaN captures indium to produce p-InGaN, improving conductivity. After the p-AlGaN layer 133 is grown, the p-type InGaN layer 134 is grown to a thickness of about 150 to 500 nm. In contrast to using higher temperatures for conventional p-GaN layer growth, Mg is used as a dopant, with growth occurring in the temperature range of about 760-800 ° C. This growth condition takes into account the possibility of decomposition of In-rich InGaN nanostructures. The TMIn flow rate is set in the range of about 80-150 sccm and the chamber pressure is maintained at about 200 Torr or less. In Mg-doped GaN grown by MOCVD in a hydrogen atmosphere, the Mg acceptor is passivated by the H acceptor, resulting in an electrically inactive Mg—H complex. A person skilled in the art understands that in this example embodiment, aside from forming the p-InGaN layer 134 below 900 ° C., the AlN layer 118 can help further prevent outdiffusion of InGaN quantum dots such as 114. Will do.

In one embodiment, in-situ annealing is performed in a nitrogen atmosphere for about 10-20 minutes, and Mg in p-type In _m Ga _1-m N with _m in the range of about 0.05-0.10 is obtained. Activate. The annealing temperature is maintained at about 20 ° C. to 50 ° C. above the growth temperature of the p-type In _m Ga _1-m N layer 134.

  In this example embodiment, the GaN layer 130 to the p-InGaN layer 134 form a p-InGaN contact structure 136.

  FIG. 2 is a schematic diagram illustrating the formation of electrical contacts on the monochromatic LED structure 100 of the example embodiment. The layer on top of the GaN layer 108 is etched using inductively coupled plasma etching (ICP). A p-contact 202 is formed on the p-InGaN layer 134 and an n-contact 204 is formed on the GaN layer 108. Using the p-contact 202 and the n-contact 204, a pn junction is formed to provide an injection current for activating the LED structure 100 to emit monochromatic light.

  In the example embodiment described above, each InGaN wetting layer 112, etc., of the quantum well structures 122, 124 can facilitate the formation of indium rich quantum dots, such as 114, and each AlN of the quantum well structures 122, 124. The layer 118 or the like can function as a cap to prevent InGaN quantum dots such as 114 from diffusing. Further, each InGaN wetting layer 112 or the like can perform better size control for forming In-rich quantum dots and providing monochromatic light. The above example embodiments can provide monochromatic LEDs that can operate in longer wavelength bands, such as for yellow, orange and / or red emission.

  FIGS. 3 (a) -3 (c) are intensity vs. wavelength graphs showing the electroluminescence spectra of yellow, orange and red LEDs, respectively, each of which is obtained using the example embodiments described above. The TMIn flow during growth of In-rich quantum dots such as 114 (FIG. 1) and the growth temperature of the InGaN quantum well layer 116 (FIG. 1) change to change the color of light emission. The graph is based on measurements obtained using an injection current of about 20 mA. From FIG. 3 (a) to FIG. 3 (c), it is observed that the intensity of each yellow, orange and red LED is relatively the same. It is also observed that the center frequencies of the respective yellow, orange and red LEDs are offset from each other by approximately 20 nm.

FIG. 4 is a schematic diagram illustrating another example embodiment of an adjustable white LED structure 400. A sapphire substrate 402 is prepared in the processing chamber. To promote GaN nucleation on the sapphire substrate 402, a low temperature buffer layer 406 is grown on the substrate 402 to a thickness of about 25 nm at a temperature range of about 520 ° C. to 550 ° C. A layer 408 of GaN with a doping concentration of 10 ¹⁸ cm ⁻³ is grown on the layer 406 at a temperature of about 900 ° C. to 1050 ° C. After layer 408 is grown, blue light emitting quantum well structure 410 is formed.

To form the blue light emitting quantum well structure 410, the GaN barrier layer 412 is formed at a temperature of about 760 ° C. to 850 ° C. with a Si doping concentration of about 2 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁸ cm ⁻³ at about 5 ° C. Growing to a thickness of 0.0-15.0 nm. After the GaN barrier layer 412 is grown, In _W Ga _1-W N having a thickness of about 2.0-4.0 nm on the barrier layer 412 to provide an indium composition of 0.1 <w <0.16. The well layer 414 is grown at a temperature of about 760 ° C to 790 ° C. After the InGaN well layer 414 is grown, a GaN cap layer 416 is grown on the InGaN well layer 414. For clarity of explanation, only one quantum well structure 410 is shown in FIG. One skilled in the art will appreciate that the steps for growing the quantum well structure 410 can be repeated, for example, 3-5 times to form an MQW structure.

After forming the blue light emitting quantum well structure 410, the GaN layer 418 is grown to a thickness of about 15-30 nm with a Si doping concentration of about 2 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ at a temperature of about 740 ° C. to 780 ° C. Let The _{p-Al y Ga 1-y} N electron blocking layer 420 containing (0.1 <y <0.3 wherein) is grown to a thickness of about 20~50nm at about 800 ℃ ~1020 ℃. TMA flow for growing a _{p-Al y Ga 1-y} N is maintained at about 40~100μ mol / min at a growth temperature of about 750 to 800 ° C.. During growth, the Cp ₂ Mg source is maintained at about 0.15 to 0.5 μmol / min. After the p-AlGaN layer 420 is grown, the p-GaN layer 422 is grown at about 900 ° C. to 1000 ° C. using Mg as a dopant. In this example embodiment, layers 418, 420 and 422 form a p-GaN contact structure 424. After forming the p-GaN contact structure 424, a GaN cap layer 426 is grown on the p-GaN contact structure 424 to a thickness of about 10-50 nm at a temperature range of about 800 ° C. to about 1020 ° C. A GaN cap layer 426 grows to “smooth” the surface of the p-GaN layer 422.

  After the GaN cap layer 426 is grown, a red / yellow light emitting quantum well structure 428 is grown. The processing steps for growing the red / yellow light emitting quantum well structure 428 are substantially the same as the processing steps described for growing the red / yellow light emitting quantum well structure 122 with respect to FIG. In this example embodiment, the TMIn flow during the growth of In-rich InGaN quantum dots and the growth temperature of the InGaN well layer are varied by about 10 ° C. to 30 ° C. so that the quantum well structure 428 has different wavelengths such as yellow or orange light. A red base color can be emitted.

  In this example embodiment, only one quantum well structure is shown in FIG. 4 for clarity of explanation. One skilled in the art will appreciate that the processing steps for growing quantum well structure 428 can be repeated, for example, 3-5 times to form an MQW structure (compare MQW structure 126 in FIG. 1).

  After the quantum well structure 428 is grown, a p-InGaN contact structure 430 is formed. The processing steps for forming the p-InGaN contact structure 430 are substantially the same as those described for forming the p-InGaN contact layer 136 with respect to FIG.

  FIG. 5 is a schematic diagram illustrating the formation of electrical contacts on the adjustable white LED structure 400 of the example embodiment described above. The layer on top of the n-GaN layer 408 is etched using inductively coupled plasma etching (ICP). Next, the layer on top of the p-GaN layer 422 is etched using ICP. An n-contact 502 is formed on the n-GaN layer 408, a p-contact 504 is formed on the p-GaN layer 422, and a p-contact 505 is formed on the p-InGaN layer of the p-InGaN contact structure 430. The Blue light emitting quantum well structure 410 is activated using a pn junction between contact 502 and contact 504, whereas yellow / red light emitting quantum well structure 428 is formed between contact 502 and contact 506. It is activated using a pn junction in between.

  In the above embodiment example, the yellow / red light emission quantum well structure 428 absorbs part of the blue light passing from the blue light emission quantum well structure 410 to the upper layer, and can re-emit light as yellow light. That is, the yellow light component from the yellow / red light emitting quantum well structure 428 causes direct carrier recombination (due to the pn junction between contact 502 and contact 506) and absorption of a portion of the blue component. From both. Further, the LED structure 400 can provide tunable white light because different injection currents can be separately supplied to the yellow / red light emitting quantum well structure 428 and the blue light emitting quantum well structure 410.

  In another example embodiment, the order of growth of the red / yellow light emitting quantum well structure and the blue light emitting quantum well structure can be reversed. Thus, in this example embodiment, a red / yellow light emitting quantum well structure is first grown on a sapphire substrate, followed by a p-InGaN contact structure, a blue light emitting quantum well structure, and a p-GaN contact structure. A p-InGaN contact structure can be used to form a pn junction to activate a red / yellow light emitting quantum well structure, and a p-GaN contact structure can be used to form another pn junction. Thus, the blue light emitting quantum well structure can be activated.

  In the above embodiment example, the yellow / red light emitting quantum well structure is grown before the blue light emitting quantum well structure. Therefore, the yellow light emitted from the yellow / red light emitting quantum well structure uses the p-InGaN contact structure. Only based on pn junctions formed (ie, without blue light absorption). In addition, the LED structure can provide tunable white light because different injection currents can be separately supplied to the yellow / red light emitting quantum well structure and the blue light emitting quantum well structure.

  FIG. 6 is a graph of intensity versus wavelength showing the electroluminescence spectrum of a white LED with “coldness” tunable. This tunable white LED has substantially the same processing conditions as the tunable white LED structure 400 (FIG. 4), except that a yellow light emitting quantum well structure is first grown, followed by a blue light emitting quantum well structure. Formed using.

  FIG. 7 is a schematic diagram illustrating an adjustable white LED structure 700 of yet another example embodiment. The LED structure 700 includes a GaN layer 701, a blue / green light emitting quantum well structure 702 grown on the GaN layer 701, a p-GaN contact structure 704 grown on the quantum well structure 702, and a p-GaN contact structure 704. And a red / yellow light emitting quantum well structure 708 grown on the GaN cap layer 706. The processing steps for forming the LED structure 700 are substantially the same as the processing steps for forming the LED structure 400 with respect to FIG. 4 except that no p-InGaN contact structure is formed on the red / yellow light emitting quantum well structure 708. Is the same.

  In this example embodiment, for clarity of illustration, FIG. 7 shows one quantum well structure for each blue / green light emitting quantum well structure 702 and red / yellow light emitting quantum well structure 708. Those skilled in the art will recognize the quantum well structures 702 and 708 during the formation of the respective quantum well structures 702 and 708 to form MQW structures for emitting blue / green light and red / yellow light, respectively. It will be appreciated that the processing steps for growth can be repeated, for example, 3-5 times (eg, compared to the MQW structure 126 of FIG. 1).

  In this example embodiment, the layer overlying GaN layer 701 is etched using inductively coupled plasma etching (ICP). The layer over p-GaN contact structure 704 is then etched using ICP. An n-contact 710 is formed on the GaN layer 701, and a p-contact 712 is formed on the p-GaN contact structure 704. Blue / green light emitting quantum well structure 702 is activated using a pn junction between contact 710 and contact 712, whereas red / yellow light emitting quantum well structure 708 is blue / green light emitting quantum well. Activation is based on absorption of blue light emitted from the well structure 702. Thus, in this example embodiment, there is no independent pn junction to activate the red / yellow light emitting quantum well structure 708.

  In the example embodiment described above, various injection currents can be supplied to the blue / green light emitting quantum well structure 702 so that the LED structure 700 can provide adjustable white light. One skilled in the art will appreciate that the red / yellow light emitting quantum well structure 708 can be indirectly “tunable” based on the amount of blue light that can be absorbed.

  In the example embodiment described above, white light is produced by mixing electroluminescent blue / green light with electroluminescent yellow / red light. One advantage provided by this example embodiment is that the p-GaN contact structure 704 is grown before the red / yellow light emitting quantum well structure 708 is grown, so that the outdiffusion of InN or In-rich nanostructures / quantum dots typically The high temperature growth and annealing of the p-GaN contact structure 704 that results in is no longer a concern. This example embodiment can provide a GaN / InGaN crystal-based structure and can achieve better color rendering compared to current technology. In this example embodiment, the GaN cap layer 706 can also prevent Mg out-diffusion from the p-GaN contact structure 704.

FIG. 8 is a schematic diagram illustrating a tunable white LED structure 800 in yet another example embodiment. A sapphire substrate 802 is prepared in the processing chamber. To promote GaN nucleation on the sapphire substrate 402, a low temperature buffer layer 806 is grown on the substrate 802 to a thickness of about 25 nm at a temperature range of about 520 ° C to 550 ° C. A layer of GaN 808 having a doping concentration of 10 ¹⁸ cm ⁻³ is grown on the layer 806 at a temperature of about 900 ° C. to 1050 ° C. After layer 808 is grown, a blue light emitting quantum well structure 810 is formed.

To form the green light emitting quantum well structure 810, the GaN barrier layer 812 is formed at a temperature of about 750 ° C. to 850 ° C. with a Si doping concentration of about 2 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁸ cm ^−3. Growing to a thickness of 0.0-15.0 nm. After the GaN barrier layer 812 is grown, an In _W Ga _1-W N well layer 814 having a thickness of about 2.0-4.0 nm is provided to provide an indium composition of 0.19 <w <0.26. Growing on the barrier layer 812 at a temperature of about 730.degree. After the InGaN well layer 814 is grown, a GaN cap layer 816 is grown on the InGaN well layer 814.

  In this embodiment, for the sake of clarity, only one green light emitting quantum well structure is shown in FIG. One skilled in the art will appreciate that the processing steps for growing quantum well structure 810 can be repeated, for example, 3-5 times to form an MQW structure.

  After forming the green light emitting quantum well structure 810, a p-GaN contact structure 818 is grown on the green light emitting quantum well structure 810. The processing steps for growing the p-GaN contact structure 818 are substantially the same as the processing steps for growing the p-GaN contact structure 424 with respect to FIG. After forming the p-GaN contact structure 818, a GaN cap layer 820 is grown on the p-GaN contact structure 818. After the GaN cap layer 820 is grown, a blue light emitting quantum well structure 822 is formed on the GaN cap layer 820.

  The processing steps for forming the blue light emitting quantum well structure 822 are substantially the same as the processing steps for forming the blue light emitting quantum well structure 410 with respect to FIG. In this embodiment, for the sake of clarity, only one blue light emitting quantum well structure is shown in FIG. One skilled in the art will appreciate that the process steps for growing the blue quantum well structure 822 can be repeated, for example, 3-5 times to form an MQW structure.

  Alternatively, the blue light emitting quantum well structure 822 can be grown first, followed by the green light emitting quantum well structure 810.

  In this embodiment, after forming the blue light emitting quantum well structure 822, another p-GaN contact structure 824 is grown on the blue light emitting quantum well structure 822. The processing steps for growing the p-GaN contact structure 824 are substantially the same as the processing steps for growing the p-GaN contact structure 424 with respect to FIG. After forming the p-GaN contact structure 824, a GaN cap layer 826 is grown on the p-GaN contact structure 824. After the GaN cap layer 826 is grown, a red light emitting quantum well structure 828 is formed on the GaN cap layer 826.

  The processing steps for forming the red light emitting quantum well structure 828 are substantially the same as the processing steps for forming the red light emitting quantum well structure 122 with respect to FIG. In this embodiment, for clarity of explanation, FIG. 8 shows only one red light emitting quantum well structure. One skilled in the art will appreciate that the process steps for growing red quantum well structure 828 can be repeated, for example, 3-5 times to form an MQW structure (compare MQW structure 126 of FIG. 1).

  FIG. 9 is a schematic diagram illustrating the formation of electrical contacts in the LED structure 800 of the example embodiment described above. The layer overlying the GaN layer 808 is etched using inductively coupled plasma etching (ICP). Following the etching of layer 808, the layers overlying p-GaN contact structure 818 and p-GaN contact structure 824 are sequentially etched using ICP. An n-contact 902 is formed on the GaN layer 808, a p-contact 904 is formed on the p-GaN contact structure 818, and a p-contact 906 is formed on the p-GaN contact structure 824. Green light emitting quantum well structure 810 is activated using a pn junction between contact 902 and contact 904, while blue light emitting quantum well structure 822 is formed between contact 902 and contact 906. It is activated using a pn junction. The red light emitting quantum well structure 828 is activated based on absorption of blue / green light emitted from the green and blue light emitting quantum well structures 810 and 822, respectively. Thus, in this example embodiment, there is no independent pn junction for activating the red light emitting quantum well structure 828.

  In the example embodiments described above, the LED structure 800 can provide tunable white light because various injection currents can be supplied to the green and blue light emitting quantum well structures 810, 822. One skilled in the art will appreciate that the red-emitting quantum well structure 828 can be indirectly “tunable” based on the amount of blue / green light that can be absorbed.

  The example embodiments described above can provide monochromatic yellow, orange and / or red LEDs that utilize indium-rich InGaN quantum dots to facilitate indium incorporation to achieve emission in longer wavelength regions. .

  FIG. 10 is a graph of current (I) versus voltage (V) showing IV measurements obtained from a yellow LED structure (see FIG. 3A) and a white LED structure (see FIG. 4). The plot 1002 is based on the measured value obtained from the yellow LED structure, and the plot 1004 is based on the measured value obtained from the white LED structure. It can be observed from plots 1002 and 1004 that each LED structure exhibits stable conventional diode characteristics.

  FIG. 11 is a scanning electron microscope (SEM) image 1102 showing the surface morphology of the white LED structure 400 with respect to FIG. As shown in the image 1102, the p-InGaN layer of the p-InGaN contact structure 430 (FIG. 4) has a porous-like surface, which gives a scattering effect, thereby causing quantum well structures such as 410 and 428 (FIG. 4) Promote light extraction from.

  FIG. 12 is a scanning electron microscope (SEM) image 1202 showing the surface morphology of the white LED structure 700 with respect to FIG. Image 1202 shows a p-contact as Ni / Au contact pad 1204 and an n-contact as Ti / Al contact pad 1208.

  FIG. 13 is a scanning electron microscope (SEM) image 1302 in which the image 1202 of FIG. 12 is enlarged. As shown in image 1302, the p-contact is in the form of a Ni / Au metal stripe, such as 1304, between which the surface 1306 of the red / yellow light emitting quantum well structure is visible.

  FIG. 14 is an intensity vs. wavelength graph 1402 showing the electroluminescence spectrum of the sample white LED structure of FIGS. Graph 1402 shows an emission peak 1404 at about 456 nm. The emission peak 1404 of emission 1408 is produced by the blue / green emission quantum well structure. Graph 1402 also shows a broad and low intensity emission 1406. Light emission 1406 is produced by a red / yellow light emitting quantum well structure. Those skilled in the art will recognize that the red / yellow light emission quantum well structure is activated based on the absorption of blue light emitted from the blue / green light emission quantum well structure, so You will understand that the strength is lower.

  FIG. 15 is a graph 1502 of current (I) versus voltage (V) showing the IV measurements obtained from the sample white LED structure of FIGS. It can be observed from graph 1502 that the white LED structure exhibits good IV characteristics with a turn-on voltage of about 3V and a current of about 60mA at about 5V.

  FIG. 16 is a flow diagram illustrating a method of fabricating an MQW structure for a light emitting diode. In step 1602, a plurality of quantum well structures are formed. Each quantum well structure includes a barrier layer and a well layer formed on the barrier layer and incorporating quantum dot nanostructures, the barrier layer and well layer including a first metal nitride based material. In step 1604, at least one of the quantum well structures is formed on the well layer to further include a capping layer, the capping layer being a second metal having a different metal component compared to the first metal nitride based material. Includes nitride based materials.

  FIG. 17 is a flow diagram illustrating a method for fabricating a light emitting diode structure. In step 1702, a red / yellow light emitting multiple quantum well (MQW) structure is formed. Each quantum well structure of the red / yellow light emitting MQW includes a barrier layer and a well layer formed on the barrier layer and incorporating a quantum dot nanostructure, the barrier layer and the well layer being a first metal nitride based material including. In step 1704, at least one of the red / yellow light emitting MQW quantum well structures is formed on the well layer to further include a capping layer, the capping layer having a different metal component compared to the first metal nitride based material. A second metal nitride-based material having: In step 1706, a blue light emitting MQW structure is formed integrally with the red / yellow light emitting MQW to emit white light from the light emitting diode structure.

  FIG. 18 is a flow diagram illustrating another method for fabricating a light emitting diode. In step 1802, a red / yellow light emitting multiple quantum well (MQW) structure is formed. Each quantum well structure of the red / yellow light emitting MQW includes a barrier layer and a well layer formed on the barrier layer and incorporating a quantum dot nanostructure, the barrier layer and the well layer being a first metal nitride based material including. In step 1804, at least one of the red / yellow light emitting MQW quantum well structures is formed on the well layer to further include a capping layer, the capping layer having a different metal component compared to the first metal nitride-based material. A second metal nitride-based material having: In step 1806, a blue light emitting MQW structure is integrally formed with the red / yellow light emitting MQW. In step 1808, a green light emitting MQW structure is formed integrally with the red / yellow light emitting MQW and blue light emitting MQW structures to emit white light from the light emitting diode structure.

  In the embodiments described above, In-rich InGaN quantum dots or nanostructures incorporated in the well layer are used to generate red, amber and / or yellow light. In order to prevent external diffusion into the GaN barrier, such as during high temperature in-situ annealing, the individual active quantum well layers are encapsulated by a thin AlN layer. To produce white light, a combination of different color MQWs can be incorporated into a single LED structure. Thus, the need to use complex circuitry to operate the devices of the described example embodiments can be eliminated. Furthermore, since no phosphor is used, the fabrication technique can be simplified, and this example embodiment presents the problem of phosphor degradation as in the case of normal RGB LEDs, and different degradation effects of different material based LEDs. Can be solved. The described example embodiments can also eliminate the use of a phosphor outer coating on the LED chip. Also, the incorporation of In-rich InGaN quantum dots in the described example embodiments can further increase recombination efficiency and provide better stability during high temperature operation and the like.

  Furthermore, in the described exemplary embodiment that can emit individual primary colors of blue, green and red from individual quantum well structures, for example, by controlling dot size and In composition, for example “cold” white, “apple” Different quality whites can be obtained, such as “white” or “warm” white.

  As explained in the background section, the production of GaN LEDs is practically difficult mainly due to the difficulty in obtaining high indium incorporation in the InGaN layer. This usually occurs due to the solid immiscibility of indium and the decomposition at high temperatures. In the example embodiment described above, a thin InGaN wetting layer is used to facilitate indium uptake during the TMI burst step. This can facilitate the formation of indium-rich InGaN quantum dots that have been found to push the emission wavelength into the red wavelength region. For example, the temperature during growth of In-rich quantum dots and InGaN wells is kept stable in order to obtain a monochromatic emission color in a longer wavelength region or the like. This temperature variation can lead to a slight change in wavelength when a voltage bias is applied. Further, regarding the temperature, when the p-GaN layer is grown at a temperature of about 900 ° C., the formed indium-rich InGaN quantum dots usually diffuse into the well layer and the like as well as into the barrier layer. . In the example embodiment described, the temperature is lowered to about 750 ° C. to about 800 ° C. during the growth of the p-InGaN layer. It will be appreciated that in situ annealing at about 800 ° C. to 850 ° C. may shift the emission wavelength due to indium diffusion within the quantum dots. Thus, in the described example embodiment, an AlN layer is used to grow a p-InGaN layer, during growth of other layers at high temperatures, and / or during in situ annealing at about 800 ° C. to 850 ° C. External diffusion from indium quantum dots can be prevented. The described example embodiments can also obtain primary color emission from GaN LEDs, which can allow better white light color rendering for solid state lighting.

  Using the example embodiments described above, signage and display lighting, keypad light guiding, digital camera flash light, PC monitor backlighting, color rendering, lighting and display purposes including solid state lighting, and automotive taillights and InGaN quantum dot LEDs can be used for many applications such as traffic lights.

  One skilled in the art can provide conventional organic LEDs (OLEDs) to provide flexible displays in yellow, orange and red, but typically OLEDs are inorganic as in this embodiment with respect to luminous flux and luminescence efficiency. You will understand that it is inferior to LED.

  Those skilled in the art will appreciate that numerous changes and / or modifications can be made to the invention shown in the form of specific embodiments without departing from the spirit and scope of the invention as broadly described. Will do. Accordingly, in all respects, this embodiment should be considered exemplary rather than limiting.

Claims (28)

A multiple quantum well (MQW) structure for a light emitting diode,
The MQW structure includes a plurality of quantum well structures, and each quantum well structure includes:
A barrier layer;
A well layer formed on the barrier layer and incorporating quantum dot nanostructures;
The barrier layer and the well layer comprise a first metal nitride based material;
A capping layer formed on the well layer, wherein at least one of the quantum well structures includes a second metal nitride-based material having a different metal element compared to the first metal nitride-based material When,
A second capping layer formed on the capping layer, wherein the second capping layer includes a third metal nitride-based material having a different metal element compared to the second metal nitride-based material. MQW structure characterized by Each quantum well structure further includes a wetting layer formed between the barrier layer and the well layer to facilitate the formation of the quantum dot nanostructure.
The MQW structure according to claim 1, wherein: The MQW structure further includes a p-type contact structure formed on the outermost structure of the plurality of quantum well structures, and the p-type contact structure is formed on the electron blocking layer and the electron blocking layer. a p-type metal nitride layer,
The MQW structure according to any one of claims 1 to 2, wherein the MQW structure is provided. The p-type metal nitride layer includes an indium (In) material;
The MQW structure according to claim 3. The p-type metal nitride layer is formed using a temperature between about 750 ° C. and 800 ° C .;
The MQW structure according to claim 4. The MQW structure further includes an n-type contact layer for making electrical contact with an n ⁺ layer underlying the plurality of quantum well structures;
The MQW structure according to any one of claims 1 to 5, wherein the MQW structure is provided. The MQW structure can emit light in a wavelength range from red to yellow;
The MQW structure according to any one of claims 1 to 6, wherein the MQW structure is provided. The MQW structure can emit red light;
The MQW structure according to any one of claims 1 to 7, wherein the MQW structure is provided. The capping layer comprises an aluminum nitride (AlN) material;
The MQW structure according to any one of claims 1 to 8, wherein the MQW structure is provided. The thickness of the capping layer is maintained at about 3 nm or less,
The MQW structure according to any one of claims 1 to 9, wherein the MQW structure is provided.   The MQW structure according to any one of claims 1 to 10, wherein the quantum dot nanostructure includes indium gallium nitride (InGaN). A light emitting diode structure,
A red / yellow emitting multiple quantum well (MQW) structure that emits light in the wavelength range from red to yellow, wherein the individual quantum well structures of the red / yellow emitting MQW include:
A barrier layer;
A well layer formed on the barrier layer and incorporating quantum dot nanostructures;
The barrier layer and the well layer comprise a first metal nitride based material;
At least one of the quantum well structures of the red / yellow emitting MQW further comprises a capping layer formed on the well layer, the capping layer being compared to the first metal nitride based material. A second metal nitride-based material having a different metal element, and further comprising a second capping layer formed on the capping layer, wherein the second capping layer comprises the second metal nitride. A third metal nitride based material having a different metal component compared to the material based material;
The light emitting diode structure further includes:
A blue light emitting MQW structure formed integrally with the red / yellow light emitting MQW to emit white light from the light emitting diode structure;
A light emitting diode structure characterized by that. The blue light emitting MQW is formed on the outermost structure of the plurality of quantum well structures of the red / yellow light emitting MQW structure.
The light emitting diode structure according to claim 12. The red / the plurality of quantum well structure of the yellow emission of MQW structure is formed on the MQW structure of the blue-emitting,
The light emitting diode structure according to claim 12. An n-type contact layer for making electrical contact with the n ⁺ layer under the red / yellow light emission and blue light emission MQW structures, and each p formed on the red / yellow light emission and blue light emission MQW structures. A p-type contact structure, each of the p-type contact structures including an electron blocking layer and a p-type metal nitride layer formed on the electron blocking layer.
The light emitting diode structure according to claim 12, wherein the light emitting diode structure is a light emitting diode structure. An n-type contact layer for making electrical contact with the n ⁺ layer under the blue light emitting MQW structure, and a p formed on the blue light emitting MQW structure for activating the blue light emitting MQW structure. A red / yellow light emitting MQW structure, which can emit light in a wavelength range from red to yellow based on absorption of blue light emission from the blue light emitting MQW structure.
The light emitting diode structure according to claim 14. The capping layer comprises an aluminum nitride (AlN) material;
The light emitting diode structure according to any one of claims 12 to 16. The thickness of the capping layer is maintained at about 3 nm or less,
The MQW structure according to any one of claims 12 to 17, wherein the MQW structure is provided.   The MQW structure according to claim 12, wherein the quantum dot nanostructure includes indium gallium nitride (InGaN). A light emitting diode structure,
A red / yellow emitting multiple quantum well (MQW) structure that emits light in the wavelength range from red to yellow, wherein the individual quantum well structures of the red / yellow emitting MQW include:
A barrier layer;
A well layer formed on the barrier layer and incorporating quantum dot nanostructures;
The barrier layer and the well layer comprise a first metal nitride based material;
At least one of the quantum well structures of the red / yellow emitting MQW further comprises a capping layer formed on the well layer, the capping layer being compared to the first metal nitride based material. A second metal nitride-based material having a different metal element, and further comprising a second capping layer formed on the capping layer, wherein the second capping layer comprises the second metal nitride. A third metal nitride based material having a different metal component compared to the material based material;
The light emitting diode structure further includes:
A blue-emitting MQW structure;
MQW structure with green emission,
The blue light emitting MQW structure and the green light emitting MQW structure are formed integrally with the red / yellow light emitting MQW to emit white light from the light emitting diode structure.
A light emitting diode structure characterized by that. The red / yellow light emitting MQW structure is formed on the blue light emitting MQW structure and the green light emitting MQW structure.
The light-emitting diode structure according to claim 20. An n-type contact layer for making electrical contact with the n ⁺ layer under the red / yellow emission, blue emission and green emission MQW structures;
P-type contact structures formed on the blue light-emitting MQW structure and the green light-emitting MQW structure, respectively, for activating the blue light-emitting MQW structure and the green light-emitting MQW structure;
Further including
Each of the p-type contact structures includes an electron blocking layer and a p-type metal nitride layer formed on the electron blocking layer, and the red / yellow light emitting MQW structure is different from the blue light emitting MQW structure. Can emit light in the wavelength range from red to yellow based on absorption of both blue emission, green emission from the green emission MQW structure, or both of these,
The light-emitting diode structure according to claim 20 or claim 21, wherein The capping layer comprises an aluminum nitride (AlN) material;
The light-emitting diode structure according to any one of claims 20 to 22, wherein the light-emitting diode structure is provided. The thickness of the capping layer is maintained at about 3 nm or less,
24. The light-emitting diode structure according to claim 20, wherein the light-emitting diode structure is a light-emitting diode structure.   25. A light emitting diode structure according to any one of claims 20 to 24, wherein the quantum dot nanostructure comprises indium gallium nitride (InGaN). A method of fabricating a multiple quantum well (MQW) structure for a light emitting diode, comprising:
A plurality of quantum well structures, each comprising a barrier layer and a well layer formed on the barrier layer and incorporating a quantum dot nanostructure, wherein the barrier layer and the well layer are based on a first metal nitride base Forming a plurality of quantum well structures comprising materials;
A capping layer on the well layer, the second metal nitride based material comprising a second metal nitride based material having a different metal element compared to the first metal nitride based material; Forming at least one of said quantum well structures to include a second capping layer formed on said capping layer comprising a third metal nitride based material having a different metal element compared to And steps to
A method comprising the steps of: A method for fabricating a light emitting diode structure comprising:
A multiple quantum well structure (MQW), each quantum well structure including a barrier layer and a well layer formed on the barrier layer and incorporating a quantum dot nanostructure, wherein the barrier layer and the well layer are first Forming a red / yellow emitting multiple quantum well structure that emits light in the wavelength range from red to yellow, comprising a metal nitride based material of:
Further seen including a capping layer on the well layer comprising a second metal-nitride based material having a metal element different compared to the first metal-nitride based material, and the second metal nitride The red / yellow light emitting material further includes a second capping layer formed on the capping layer, the third capping layer comprising a third metal nitride based material having a different metal component compared to the material based material . Forming at least one of said quantum well structures of MQW;
Forming a blue emitting MQW structure integrally with the red / yellow emitting MQW to emit white light from the light emitting diode structure;
A method comprising the steps of: A method for fabricating a light emitting diode structure comprising:
A multiple quantum well structure (MQW), each quantum well structure including a barrier layer and a well layer formed on the barrier layer and incorporating a quantum dot nanostructure, wherein the barrier layer and the well layer are first Forming a red / yellow emitting multiple quantum well structure that emits light in the wavelength range from red to yellow, comprising a metal nitride based material of:
Further seen including a capping layer on the well layer comprising a second metal-nitride based material having a metal element different compared to the first metal-nitride based material, and the second metal nitride a third metal nitride based material having a different metal components as compared to the object-based material, the second capping layer further contains useless formed capping layer, the red / yellow light emitting MQW Forming at least one of said quantum well structures of:
Forming a blue light emitting MQW structure integrally with the red / yellow light emitting MQW;
Forming a green light emitting MQW structure integrally with the red / yellow light emitting MQW structure and the blue light emitting MQW structure to emit white light from the light emitting diode structure;
A method comprising the steps of:

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